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Discussion Starter #1
Hi folks,

I changed the plugs in my '91 SE-R recently. They are Bosch platinum plugs and had 50k+ on them.

The first plug (pass side) looked worn but fine (center electrode eroded). The middle two plugs had an odd varnish on the nut part (above the threads). The fourth (driver's) had an even more odd yellowish powder baked on the nut part (again, above the threads). Also the anti-seize on the fourth plug was obviously burned up. I assume that this cylinder is running hot, but the yellow powder is throwing me off. Do I also have an antifreeze leak (head gasket)? Why would the residue be above the threads?

I'm thinking a clogged injector (running lean/hot) and maybe a head gasket leak (antifreeze). Any thoughts?

I tried to atatch a picture, but it seems I am not allowed. I can email one if someone has a theory.

Many thanks,
Bman
 

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sleeper
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The varnish could be from oil. Sometimes, you get a little bit of oil that leaks from the valve cover and into the spark plug wells. I doubt it's coolant.
 

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P10 Geek
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Bman91SER said:
Hi folks,

I changed the plugs in my '91 SE-R recently. They are Bosch platinum plugs and had 50k+ on them.
Well, initially I would say the first issue is that they are Bosch platinums. These are proven not to be a good choice for SR20's. Second thought is they have 50,000 miles on them. You might get variances in how the plugs are sparking when they start to get high mileage on them even if they are platinums.

I would suggest you get yourself a set of NGK's (platinum or copper), run around on those for a few thousand miles, then check all 4 plug's conditions at that time. Then you will see if you have any variances and/or issues to be concerned with.
 

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Discussion Starter #4
Hi folks,

I was a bit suspicious that choice of spark plugs would make much of a difference, but since NGK coppers are $1.60, I swapped out my new Bosch platinums for NGKs this past weekend.

Wow! Idle is much smoother, warm up cycle hesitation is reduced, and I have lost the "flat spot" I had at 3500 RPM. I'll watch to see if all cylinders burn evenly, but I already see a difference.

Thanks for the good advice.
Bman
 

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NismoPC said:
Well, initially I would say the first issue is that they are Bosch platinums. These are proven not to be a good choice for SR20's. Second thought is they have 50,000 miles on them. You might get variances in how the plugs are sparking when they start to get high mileage on them even if they are platinums.

I would suggest you get yourself a set of NGK's (platinum or copper), run around on those for a few thousand miles, then check all 4 plug's conditions at that time. Then you will see if you have any variances and/or issues to be concerned with.
Yeah, what he said. ;)
 
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